Purified cholera enterotoxin and heat labile enterotoxin(s) of E. coli stimulate cell membrane adenylate cyclase and produce a cellular response characteristic in any given tissue of increased cyclic AMP. In addition these toxins increase the response by several tissues including fat cells to epinephrine. We have demonstrated our activity in cytosol that enhances the response of fat cell membrane preparations to epinephrine. This activity disappears from the cell sap within 60 minutes of exposure of cells to cholera toxin. A significant change was observed within 15 minutes. This correlates with increased membrane adenylate cyclase response to epinephrine in toxin-treated cells. We are studying this effect by toxin in relation to the known effects of toxin on cells. In addition we have found that in the presence of fresh cytosol, toxin will stimulate broken cell preparations directly. Further studies of the cytosol activities important in permitting broken cells to respond are being carried out.